The only statewide gun legislation on the ballot this Election Day was approved by 60 percent of Washington voters. Initiative 1639 will tighten laws on semi-automatic rifles in the state.

The law will raise the legal age to purchase semi-automatic rifles to 21, impose a 10-day waiting period on purchases, require an annual background check and mandate purchasers to take a firearms training course.

The measure also created a new class of crime called “community endangerment,” which requires gun owners to store their firearms so they don’t get into the hands of someone who isn’t permitted to access it, such as a felon or child.

If a firearm does get into the wrong hands and that firearm is displayed in public, discharged, or used to commit a crime, the owner can be charged with misdemeanor or felony community endangerment.

Steve Paolini, 22, is the initiative’s campaign manager. Speaking at a reception after Tuesday night’s results were announced, he said he expects his generation to champion gun regulations.

“My generation has been defined by gun violence. It has been defined by American gun violence,” Paolini said. “We have been defined by continued and repeated inaction by our elected officials.”

Once the law is fully implemented, Washington will join California, Hawaii and Massachusetts as states with some of the country’s strictest gun laws.

Critics of the legislation say that the law is misguided in treating small .22 caliber rifles the same as larger AR-15s. They also say that it discriminates based on age, something opponents will likely argue is unconstitutional.

The Washington campaign highlights some of the big money that is starting to pour into gun regulation efforts across the country. Initiative 1639 received more than $5.5 million from donors, including former New York City Mayor Michael Bloomberg’s organization Everytown for Gun Safety, as well as from recently deceased Microsoft co-founder and philanthropist Paul Allen, former Microsoft CEO Steve Ballmer and venture capitalist Nick Hanauer.

By comparison, opposition groups led by the National Rifle Association and the Bellevue, Washington-based Citizens Committee for the Right to Keep and Bear Arms raised about $622,000.

The age restriction will take effect on Jan. 1, 2019, while the rest of the law will go into effect July 1, 2019.